<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>利用border画直角三角形</title>
    <style>
        .right-angle-triangle{
            width: 0;
            border-top: 100px solid black;
            border-right: 100px solid transparent;
        }
    </style>
</head>
<body>
    <div class="right-angle-triangle">

    </div>
    
</body>
</html>